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    Subject[PATCH 4.19 026/131] rxrpc: Fix notification call on completion of discarded calls
    Date
    From: David Howells <dhowells@redhat.com>

    [ Upstream commit 0041cd5a50442db6e456b145892a0eaf2dff061f ]

    When preallocated service calls are being discarded, they're passed to
    ->discard_new_call() to have the caller clean up any attached higher-layer
    preallocated pieces before being marked completed. However, the act of
    marking them completed now invokes the call's notification function - which
    causes a problem because that function might assume that the previously
    freed pieces of memory are still there.

    Fix this by setting a dummy notification function on the socket after
    calling ->discard_new_call().

    This results in the following kasan message when the kafs module is
    removed.

    ==================================================================
    BUG: KASAN: use-after-free in afs_wake_up_async_call+0x6aa/0x770 fs/afs/rxrpc.c:707
    Write of size 1 at addr ffff8880946c39e4 by task kworker/u4:1/21

    CPU: 0 PID: 21 Comm: kworker/u4:1 Not tainted 5.8.0-rc1-syzkaller #0
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
    Workqueue: netns cleanup_net
    Call Trace:
    __dump_stack lib/dump_stack.c:77 [inline]
    dump_stack+0x18f/0x20d lib/dump_stack.c:118
    print_address_description.constprop.0.cold+0xd3/0x413 mm/kasan/report.c:383
    __kasan_report mm/kasan/report.c:513 [inline]
    kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
    afs_wake_up_async_call+0x6aa/0x770 fs/afs/rxrpc.c:707
    rxrpc_notify_socket+0x1db/0x5d0 net/rxrpc/recvmsg.c:40
    __rxrpc_set_call_completion.part.0+0x172/0x410 net/rxrpc/recvmsg.c:76
    __rxrpc_call_completed net/rxrpc/recvmsg.c:112 [inline]
    rxrpc_call_completed+0xca/0xf0 net/rxrpc/recvmsg.c:111
    rxrpc_discard_prealloc+0x781/0xab0 net/rxrpc/call_accept.c:233
    rxrpc_listen+0x147/0x360 net/rxrpc/af_rxrpc.c:245
    afs_close_socket+0x95/0x320 fs/afs/rxrpc.c:110
    afs_net_exit+0x1bc/0x310 fs/afs/main.c:155
    ops_exit_list.isra.0+0xa8/0x150 net/core/net_namespace.c:186
    cleanup_net+0x511/0xa50 net/core/net_namespace.c:603
    process_one_work+0x965/0x1690 kernel/workqueue.c:2269
    worker_thread+0x96/0xe10 kernel/workqueue.c:2415
    kthread+0x3b5/0x4a0 kernel/kthread.c:291
    ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

    Allocated by task 6820:
    save_stack+0x1b/0x40 mm/kasan/common.c:48
    set_track mm/kasan/common.c:56 [inline]
    __kasan_kmalloc mm/kasan/common.c:494 [inline]
    __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:467
    kmem_cache_alloc_trace+0x153/0x7d0 mm/slab.c:3551
    kmalloc include/linux/slab.h:555 [inline]
    kzalloc include/linux/slab.h:669 [inline]
    afs_alloc_call+0x55/0x630 fs/afs/rxrpc.c:141
    afs_charge_preallocation+0xe9/0x2d0 fs/afs/rxrpc.c:757
    afs_open_socket+0x292/0x360 fs/afs/rxrpc.c:92
    afs_net_init+0xa6c/0xe30 fs/afs/main.c:125
    ops_init+0xaf/0x420 net/core/net_namespace.c:151
    setup_net+0x2de/0x860 net/core/net_namespace.c:341
    copy_net_ns+0x293/0x590 net/core/net_namespace.c:482
    create_new_namespaces+0x3fb/0xb30 kernel/nsproxy.c:110
    unshare_nsproxy_namespaces+0xbd/0x1f0 kernel/nsproxy.c:231
    ksys_unshare+0x43d/0x8e0 kernel/fork.c:2983
    __do_sys_unshare kernel/fork.c:3051 [inline]
    __se_sys_unshare kernel/fork.c:3049 [inline]
    __x64_sys_unshare+0x2d/0x40 kernel/fork.c:3049
    do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:359
    entry_SYSCALL_64_after_hwframe+0x44/0xa9

    Freed by task 21:
    save_stack+0x1b/0x40 mm/kasan/common.c:48
    set_track mm/kasan/common.c:56 [inline]
    kasan_set_free_info mm/kasan/common.c:316 [inline]
    __kasan_slab_free+0xf7/0x140 mm/kasan/common.c:455
    __cache_free mm/slab.c:3426 [inline]
    kfree+0x109/0x2b0 mm/slab.c:3757
    afs_put_call+0x585/0xa40 fs/afs/rxrpc.c:190
    rxrpc_discard_prealloc+0x764/0xab0 net/rxrpc/call_accept.c:230
    rxrpc_listen+0x147/0x360 net/rxrpc/af_rxrpc.c:245
    afs_close_socket+0x95/0x320 fs/afs/rxrpc.c:110
    afs_net_exit+0x1bc/0x310 fs/afs/main.c:155
    ops_exit_list.isra.0+0xa8/0x150 net/core/net_namespace.c:186
    cleanup_net+0x511/0xa50 net/core/net_namespace.c:603
    process_one_work+0x965/0x1690 kernel/workqueue.c:2269
    worker_thread+0x96/0xe10 kernel/workqueue.c:2415
    kthread+0x3b5/0x4a0 kernel/kthread.c:291
    ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

    The buggy address belongs to the object at ffff8880946c3800
    which belongs to the cache kmalloc-1k of size 1024
    The buggy address is located 484 bytes inside of
    1024-byte region [ffff8880946c3800, ffff8880946c3c00)
    The buggy address belongs to the page:
    page:ffffea000251b0c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0
    flags: 0xfffe0000000200(slab)
    raw: 00fffe0000000200 ffffea0002546508 ffffea00024fa248 ffff8880aa000c40
    raw: 0000000000000000 ffff8880946c3000 0000000100000002 0000000000000000
    page dumped because: kasan: bad access detected

    Memory state around the buggy address:
    ffff8880946c3880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    ffff8880946c3900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    >ffff8880946c3980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    ^
    ffff8880946c3a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    ffff8880946c3a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    ==================================================================

    Reported-by: syzbot+d3eccef36ddbd02713e9@syzkaller.appspotmail.com
    Fixes: 5ac0d62226a0 ("rxrpc: Fix missing notification")
    Signed-off-by: David Howells <dhowells@redhat.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/rxrpc/call_accept.c | 7 +++++++
    1 file changed, 7 insertions(+)

    diff --git a/net/rxrpc/call_accept.c b/net/rxrpc/call_accept.c
    index c5566bc4aaca3..7778f0fb48cf4 100644
    --- a/net/rxrpc/call_accept.c
    +++ b/net/rxrpc/call_accept.c
    @@ -26,6 +26,11 @@
    #include <net/ip.h>
    #include "ar-internal.h"

    +static void rxrpc_dummy_notify(struct sock *sk, struct rxrpc_call *call,
    + unsigned long user_call_ID)
    +{
    +}
    +
    /*
    * Preallocate a single service call, connection and peer and, if possible,
    * give them a user ID and attach the user's side of the ID to them.
    @@ -232,6 +237,8 @@ void rxrpc_discard_prealloc(struct rxrpc_sock *rx)
    if (rx->discard_new_call) {
    _debug("discard %lx", call->user_call_ID);
    rx->discard_new_call(call, call->user_call_ID);
    + if (call->notify_rx)
    + call->notify_rx = rxrpc_dummy_notify;
    rxrpc_put_call(call, rxrpc_call_put_kernel);
    }
    rxrpc_call_completed(call);
    --
    2.25.1
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